Re: [PATCH] proc/wchan: Use printk format instead of lookup_symbol_name()

[Andrew Morton]

On Thu, 17 Dec 2020 17:54:13 +0100 Helge Deller <del...@gmx.de> wrote:

> To resolve the symbol fuction name for wchan, use the printk format
> specifier %ps instead of manually looking up the symbol function name
> via lookup_symbol_name().
> 
> Signed-off-by: Helge Deller <del...@gmx.de>
> 

Please don't forget the "^---$" to separate the changelog from the
diff.

>  #include <linux/module.h>
> @@ -386,19 +385,17 @@ static int proc_pid_wchan(struct seq_file *m, struct 
> pid_namespace *ns,
>                         struct pid *pid, struct task_struct *task)
>  {
>       unsigned long wchan;
> -     char symname[KSYM_NAME_LEN];
> 
> -     if (!ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS))
> -             goto print0;
> +     if (ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS))
> +             wchan = get_wchan(task);
> +     else
> +             wchan = 0;
> 
> -     wchan = get_wchan(task);
> -     if (wchan && !lookup_symbol_name(wchan, symname)) {
> -             seq_puts(m, symname);
> -             return 0;
> -     }
> +     if (wchan)
> +             seq_printf(m, "%ps", (void *) wchan);
> +     else
> +             seq_putc(m, '0');
> 
> -print0:
> -     seq_putc(m, '0');
>       return 0;
>  }

We can simplify this further?

static int proc_pid_wchan(struct seq_file *m, struct pid_namespace *ns,
                          struct pid *pid, struct task_struct *task)
{
        if (ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS))
                seq_printf(m, "%ps", (void *)get_wchan(task));
        else
                seq_putc(m, '0');

        return 0;
}


--- 
a/fs/proc/base.c~proc-wchan-use-printk-format-instead-of-lookup_symbol_name-fix
+++ a/fs/proc/base.c
@@ -384,15 +384,8 @@ static const struct file_operations proc
 static int proc_pid_wchan(struct seq_file *m, struct pid_namespace *ns,
                          struct pid *pid, struct task_struct *task)
 {
-       unsigned long wchan;
-
        if (ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS))
-               wchan = get_wchan(task);
-       else
-               wchan = 0;
-
-       if (wchan)
-               seq_printf(m, "%ps", (void *) wchan);
+               seq_printf(m, "%ps", (void *)get_wchan(task));
        else
                seq_putc(m, '0');
 
_